Deaths directly or indirectly attributable to the first wave of Covid-19 infections across 21 wealthy nations earlier this year exceeded government tallies by 20 percent on average, according to a study published Wednesday.
Looking at the period from mid-February through May 2020, researchers reported 206,000 more deaths than would have been expected without the pandemic.
But only 167,148 were officially traced to the coronavirus that has swept the globe since the start of the year, infecting tens of millions.
Many of the roughly 40,000 unaccounted-for deaths were due to Covid-19 but not listed as such, especially early in the pandemic when overwhelmed hospitals in some nations were unable to systematically test patients.
Others could have resulted from disruptions in health care, such as missed treatments for cancer or lack of access to emergency services following a heart attack or accident.
"The impacts of the pandemic on deaths goes beyond infection alone because it affects death in 'indirect' ways," senior author Majid Ezzati, a professor of global environmental health at Imperial College London, told AFP.
The excess mortality from all causes for the 15-week period varied sharply across nations examined.
It was highest in Spain and England and Wales, which each saw 100 "extra" deaths per 100,000 people, about 37 percent above what would been expected absent the pandemic.
- Deceptively difficult -
England and Wales, Spain and Italy accounted for three-quarters of the total number of excess deaths, the study found. Belgium and Scotland were also hit hard.
At the other end of the spectrum, countries that showed no detectable rise in deaths in the spring included Bulgaria, New Zealand, Slovakia, Australia, the Czech Republic, Hungary, Poland, Norway, Denmark and Finland.
The rest of the countries analysed -- Austria, Switzerland, Portugal, France, the Netherlands and Sweden -- fell somewhere in between.
The 206,000 excess deaths were almost evenly divided between men and women, a finding at odds with death rates reported in hospitals, where a significantly higher proportion of victims were male.
Figuring out exactly how many people have died during a pandemic is deceptively difficult, scientists say.
Tallies limited to "confirmed cases" will miss many Covid deaths that were misdiagnosed or not tested in the first place.
Methods also vary.
"What counts as Covid-19 death is defined differently in different countries," said Kevin McConway, a professor of applied statistics at Britain's Open University, who was not involved in the study.
- Building a better model -
Such an approach generally compares the number of deaths during a pandemic or other catastrophe to the same period across previous years.
But Ezzati and colleagues went further, building a model "that accounts for things like seasonality, trend and temperature to predict the number that would be expected if there had been no pandemic," he explained.
Countries that move quickly to implement lockdowns were likely to see shorter periods of excess death, the study showed.
There was also a strong statistical link between higher spending per capita on healthcare and lower rates of excess death during the first wave of infections.
"A strong and equitable health system is the only way to tackle existing inequalities, and to make the nation resilient to future pandemics," Ezzati said.
Meanwhile a study published Monday in the Journal of the American Medical Association (JAMA), also based on an analysis of death records, found that for every two deaths in the United States directly attributed to Covid-19 from March through July, a third American also died as a result of the pandemic.
Deaths from all causes in the United States -- normally stable from year to year -- were up 20 percent during the period examined, the study found.
The data also showed that the first states to ease restrictions on public gatherings, in April and May, also saw more rapid surges in infections and deaths in the following months.
"The high count in the Sun Belt" -- including Texas, Arizona and Florida -- "show us the grave consequences of how some states responded to the pandemic," said lead author Steven Woolf, director emeritus of the Center on Society and Health at Virginia Commonwealth University.